Carrier 48GH - Manual (Page 10)

Table 3 — Rated Gas Inputs (Btuh) for Various
Burner Orifices at Indicated Manifold Pressures*
MANIFOLD NATURAL GAS LP (Propan
NUMBER
PRESSURE - — — - ■ - . -
OF
(in. wg) Orifice Orifice
ORIFICES
Nat LP (Propane) (Btuh)t
2 3 5 105
LH32DB-205t (Min) 40,000 LH32DB-201
LH32DB-207 (Max) 50,000 LH32DB-060
3 3 5 105
LH32DB-205t (Min) 60,000 LH32DB-201
LH32DB-207 (Max) 75,000 LH32DB-060
4 3 5 105
LH32DB^200t (Min) 80,000 LH32DB-201
LH32DB-096 (Max) 100,000 LH32DB-060
5 3 5 105
LH32DB-200t (Min) 100,000 LH32DB-201
LH32DB-096 (Max) 125,000 LH32DB-060
LH32DB-200t (Min) 120,000 LH32DB-201
6 3 5 10 5 - --------
------
-
LH32DB-096 (Max) 150,000 LH32DB-060
MODEL
NO. 48
GL018,024,030
GH024,030
GL036,042
GH042; GL048
GH036,048
GL060
GH060
‘Data in this table is based on altitudes from sea level up to either
7000 ft above sea level at the minimum rated input, or 2000 ft
above sea level at the maximum rated input For higher altitudes,
follow the recommendations of national and local codes
tGas inputs for natural gas are based on a heating value of
1050 Btu/ft^ with a specific gravity of 0 65 at the factory-set
GAS ___
Heating
Input
(Btuh)t
40.000
50.000
60.000
75,000
so’ooo^
100,000
100 , 000 ^
125.000
120
,
000
^
150.000
manifold pressure of 3 5 in wg Gas inputs for LP (propane) gas
are based on a heating value of 2500 Btu/ft^ with a specific
gravity of 1 5 at a manifold pressure of 10 5 in wg
JThese natural gas burner orifices are the factory-supplied
orifices All other natural gas orifices shown are optional field-
supplied orifices
The minimum and maximum rated gas inputs
shown in Table 3 are for altitudes from sea level up
to either 7000 ft above sea level at minimum input,
or 2000 ft above sea level at maximum input. These
inputs are based on natural gas with a heating value
of 1050 Btu per cubic foot at 0.65 specific gravity,
or LP (propane) gas with a heating value of 2500 Btu
per cubic foot at 1.5 specific gravity. For elevations
above either 7000 ft at minimum input or 2000 ft
at maximum input, reduce ratings 4% of maximum
input for each 1000 ft above sea level. When gas
supply being used has a different heating value or
specific gravity, refer to Carrier training and
application materials, national and local codes, or
contact your Carrier dealer to determine required
orifice size.
ADJUSTING GAS INPUT
CAUTION: When adjusting the gas input, do
not change manifold pressure more ihan
03 in. wg above or below setting shown in
Table 3. If larger adjustments are required,
change burner orifices following recommenda­
tions of national and local codes.
Gas input to unit is adjusted by changing mani­
fold pressure. Use REG ADJ screw on gas valve to
change manifold pressure as follows:
To increase input: Turn screw clockwise.
To decrease input: Turn screw counterclockwise.
Gas input can be determined and adjusted by
using one of tbe following 2 recommended methods:
1. Measuring gas flow at meter.
2. Measuring manifold pressure.
Measuring Gas Flow at Meter
NOTE: All other gas appliances that use the same
meter must be turned off when the gas flow is
measured at the meter.
Proceed as follows to measure gas flow at meter
to determine gas input:
a. Determine number of seconds for gas meter test
dial to make one revolution.
b. Divide number of seconds in step a into 3600
(number of seconds in an hour).
c. Multiply result of step b by number of cu ft
shown for one revolution of test dial to obtain
cu ft of gas flow per hour.
d. Multiply result from step cby Btuh heating value
of gas to obtain total measured input in Btuh.
Compare this value with input shown in Table 3.
NOTE: Consult local gas supplier if heating value of
gas is not known.
Example: Assume that size of the test dial is 1 cu ft,
one revolution takes 30 seconds, and heating value
of gas is 1050 Btuh per cubic foot, then proceed
as follows:
a. 30 seconds to complete one revolution.
b. 30 divided into 3600 equals 120.
c. 120 times 1 equals 120 cu ft of gas flow per hour.
d. 120 times 1050 equals 126,000 Btuh input.
If desired gas input is 125,000 Btuh, only a minor
change in manifold pressure is required.
Measuring Manifold Pressure — When heating
value of gas is significantly more or less than design
value, or slight manifold pressure changes are
necessary for other reasons, manifold pressure
may be changed to adjust gas input. Use a water
manometer to measure manifold pressure. If a
spring manometer is used, make sure manometer
is calibrated.
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